Electric fuse assembly



Oct. 15, 1957 M. M. LEAR, JR

ELECTRIC FUSE ASSEMBLY Filed Oct. 6, 1953 INVENTOR Maz/[ea 7',

.EN m" Zia/un, @naw u 5ml ATTORNEYS ELECTRIC FUSE ASSEMBLY Max M. Lear, Jr., Lakewood, N. Y., assigner, by mesne assignments, to Monarch Electric Corporation, laines town, N. Y., a corporation of Delaware Application October 6, 1953, Serial N o. 384,500

4 Claims. (Cl. 200-131) This invention relates to electric fuse assemblies, and is more particularly concerned with clamping structures included in such assemblies for holding renewable fuse links.

A feature of the invention is the provision of a clamping device which may be employed with fuse links having notches at their ends or with fuse links having unnotched ends.

Another feature is the provision of a clamping device having locating parts to assure proper positioning of the clamp and of fuse links.

A further feature is the provision of a clamping device associated with heat-dissipating elements and effective in conjunction with a fuse link for determining the operating condition at which the fuse link will act.

With these and other features and objects in view, as will appear in the course of the following description and claims, an illustrative form of the invention is shown on the accompanying drawings, in which:

Fig. l is an axial section through a cartridge type of fuse structure including the clamping and heat-dissipating elements, and with an unnotched fuse link in position.

Fig. 2 is a top plan view of the removable internal structure of Fig. l.

Fig. 3 is a perspective view of a clamping element.

Fig. 4 is a view showing a part of the clamping structures with an end-notched fuse link in position.

Fig. 5 is a perspective view of an unnotched fuse link as used in Figs. 1 and 2.

Fig. 6 is a perspective view of an end-notched fuse link as shown in Fig. 4.

In the drawings, an outer sleeve 10, for example of an insulating and tire-resistant material such as vulcanized liber, has secured therein the end ferrules 11, 12 of metal such as brass, each having an external thread for receiving the respective annular end cap 13, 14. outer bailles or closures 15, 16 are provided within the cap 13 and held thereby against the end of the ferrule 11: these baffles have apertures 17, 18 through which extends one terminal blade 20 of a removable internal structure. The end cap 14 similarly contains a baffle or closure plate 21. lt is preferred to form the end caps with a thinned outer end, so that the bailles rest against an internal shoulder, and then to spin or curl this thinned end inward to engage the outer face of the baille, wherewith the end cap 14 can be rotated relative to the baille 21.

The removable internal assembly has the terminal blades 20, 25 which are received by the clips of the usual fuse block and serve for the passage of the electric current. Each blade has a narrower portion 26 located within the sleeve when the parts are assembled, whereby shoulders 27 are provided against which bear the baffle plates 2S, 29. At one end the baille plate 28 conforms to the baille and upon assembly is located in the plane of the baille 15: at this end a second inner baille 30 is provided of circular shape and size to fit within the end ferrule 11 with an annular space through which the heated gases may pass and move along a tortuous path Inner and States Pater 2 provided by the balles and therewith be cooled before gaining the outer atmosphere.

At the other end, the bahle 29 rests against the end of the ferrule 12 after assembly; and a second inner baille 31, of a size slightly smaller than the inside of the ferrule 12, has projecting lugs 32 which lit in notches 33 of the ferrule 12.

The battles 3@ and 29, 31 have apertures closely receiving the respective blade portion 26 and are held "rmly against the shoulders 27 by staked metal 34 displaced from these portions.

The end terminal and baille assemblies are held rigidly together and at distances such that the inner baffles 28, 29 are in proper position in the ferrules and against the outer bailles, by a bridge 4i? of insulating material such as vulcanized fiber, with screws 41 which are threaded into the respective blade portions 26. Between the portions 26 and the bridge 40, at each end, are provided the heat-dissipating fins 42 which have apertures for the screws 41: these ns may be of flat heat conductive metal stock and are positioned parallel to one another and to the portions 2e and bridge 40, spacing washers 43 being employed to ilX the relative positions.

The tins 42 also have apertures for receiving the heads of clamping bolts 5d which extend through apertures of the clade portions 2t?, and through apertures in the clamp locks 51, so that the associated nuts SZ and washers 53 are effective to draw the,` blocks 51 toward the respective blade portions 2o. As shown in Fig. 3, each clamp block 51 has a foot 55 with projecting lugs 56 for entering the alining recesses S7 in the blade portion 26 so that the blocks S1 are fixed in position against rotation about the axis of the respective bolt dit when the nut 52. is tightened. This foot 55 bears against the blade portion 25 closely adjacent the end of the screw i1 so that heat conduction to the ilns 42 along the metal screws is immediate. Each block has a rebate 55S to provide a shoulder cooperative with a fuse link for controlling the positioning of this fuse link and assuring that adequate contact surface areas are engaged for safe transmission of the rated amperage and to assure heat conduction from the fuse link into the clamping parts. Each block 51 has its central part, adjacent the bolt dit, spaced from the blade portion 26 to aord ventilation and to assure that the clamping elfo-rt is exerted upon the fuse end and the foot 55.

The fuse link in Figs. l, 2 and 5 has the heat-absorption portions 6d, 61 which are separated by a fusible portion e2 of narrower and thinner cross-section. End contact portions 63, are separated from the portions 60, 61 by fusible portions o5, do of narrower and thinner cross section than the portion 62. Such links may be formed intergrally, by a die-casting operation, from zinc.

The fuse link of Pig. 6 has the general body 70 with lateral notches 71 dividing it into a succession of portions of greater and lesser cross-section. The ends have the notches TF2, 73 which are received around the bolts 50. Since such links are of differing thickness according to the amperage to be tolerated, the clamp blocks 51 are reversed in position, Fig. 4, in such cases, to give a firm and solid seating for safe conduction of the current and heat.

ln operation with Figs. l and 2, if the current gradually increases, the heating effects likewise increase; but the heat conducted away from the smaller sections which exhibit the highest resistance and heating effects, with the portions 6d, 61, o3, 64, and thence are dissipated by direct radiation or by conduction to the blade portions 2d and thence to the fins 41 or the outer blade portions 2t), 25, for radiant dissipation. Ultimately with such slowly increasing current values, or after an essentially deilnite time interval at a current intensity above that continuously tolerated (i. e. the rated capacity), the

radiation losses are insuicient to `dissipate the heat, and the fuse link melts or blows at a smaller section, thereby interrupting the current ilow. Such delayed fuse action is known in the artbut the present employment of clamping elements which effect withdrawal of heat from an end block 63, 64, closely adjacent a portion of small section permits a control upon the condition at which such small section will melt. In the event of a sudden high current ow, as with a short circuit, the link melts at once, as there is insulicient time for significant heat conduction.

The operation with Fig. 4 is the normal one for such fuse links.

It is obvious that the illustrative form is not restrictive, and that the invention may be employed in many ways within the scope ofthe appended claims.

What is claimed is:

1. In a fuse assembly having terminal conductor members and a fuse link connecting said terminalmembers, said fuse link having a contact portion at its end, the combination of a clamp block of electrically and thermally conductive material, said block having a surface which at one end of the block has an area in electrically and thermally conductive bearing relation with the fuse link, said block having a rebate on said surface for providing the area of said bearing relation, said rebate providing n shoulder for abutting a surface of the fuse link and locating the same upon the said terminal member, said block having at its other end a foot engaged with said terminal member, said surface being spaced from said terminal member for the portion between the fuse link and the foot, said terminal member being apertured, a clamp bolt engaged in a said aperture and passing through said clamp block and through the said spaced part of the surface thereof, and a locating part on said foot engaged in another said aperture for preventing rotation of the block about the bolt axis, said clamp bolt being effective to hold said fuse link in electrically and thermally conductive relation with both the terminal member and the block.

2. In a fuse assembly having a casing sleeve and endclosing means therefor, terminal conductor members and parts within the sleeve and parts projecting through the end-closing means at the ends of the sleeve and supported thereby, a fuse link within the sleeve and extending between the terminal conductor members and electrically connected thereto, a plurality of heat-conductive and heat-dissipating fins located within the sleeve and positioned longitudinal of the sleeve and parallel to the fuse link, spacing means between the fins, and a metal nclamping means engaged in a said terminal member and engaging and holding said fins in heat-conductive relation to said terminal member.

3. In a fuse assembly having a casing sleeve and endclosing means therefor, terminal conductor members and parts within the sleeve and parts projecting through the end-closing means at the ends of the sleeve and supported thereby, a fuse link within the sleeve and extending between the terminal conductor members and electrically connected thereto, a plurality of heat-conductive and heat-dissipating tins located within the sleeve and positioned longitudinal of the sleeve and parallel to the fuse link, spacing means between the tins, an insulating bridge intervening between said terminal members and spaced therefrom, and a metal clamping means engaged with the said bridge and in a said terminal member and effective to clamp the ins between the said bridge and said terminal member and in heat-conductive relation with the said terminal member.

4. In a fuse assembly having a casing sleeve and endclosing means therefor, apertural terminal conductor members and parts within the sleeve and parts projecting through the end-closing means at the ends of the sleeve and supported thereby, a fuse link within the sleeve and extending between the terminal conductor members and electrically connected thereto, clamping blocks each comprising a metal body having at one end a foot for engaging each of the terminal members, said foot having a projecting part for entering a first aperture of the terminal member, said body having at the other end a rebate for receiving the fuse link with a rebate wall bearing upon the fuse link, the rebate providing a shoulder for engaging and locating the adjacent end of the fuse link, said block having between the said foot and the said shoulder a bolt-receiving aperture for alinement with a second aperture of the terminal member when the projecting part is in the rst aperture.

References Cited in the tile of this patent UNITED STATES PATENTS 682,786 Caldwell Sept. 17, 1901 1,282,606 Lutz Oct. 22, 1918 1,405,254 Baker Jan. 31, 1922 1,406,434 Baker Feb. 14, 1922 1,455,566 Briggs ,May 15, 1923 1,537,296 Gearhart May 12, 1925 1,623,531 Dubilier Apr. 5, 1927 1,861,267 Frank May 21, 1932 2,198,663 Floten Apr. 30, 1940 2,247,826 Weeks July 1, 1941 2,308,435 Wood Jan. 12, 1943 2,556,018 Von Hoorn June 5, 1951 2,658,125 Whitfield Nov. 3, 1953 

